Research database

We aim at providing a novel framework for the study of dense liquid-liquid emulsions. Dense emulsions are at the crossroads between academic research and practical applications (e.g., polymer production, crude oil recovery/transportation, liquid-liquid extraction processes) and their modeling poses major challenges. These are due to a partial knowledge of the complex multiscale physics that stems from the interaction between fluid dynamics and interfacial phenomena, translating into poor model predictions under realistic process conditions. One example is the drop size distribution (DSD), that determines the efficacy of controlled delivery systems in personal care and pharmaceutical products, or the final properties of polymer particles produced via emulsification. No physics-based model is available for the coalescence and breakup kernels needed to evaluate the DSD evolution and predict the rheological properties of the emulsion. To advance current knowledge and build the proposed framework, we will combine sophisticated computational methods with state-of-the-art experimental techniques (PIV, electrical resistance tomography, laser diffraction analysis), blending technology-driven objectives with original research developments. We will carry out simulations at the near-interface scale considering a sharp-interface approach to investigate the bulk rheology produced by collective drop behavior in viscous flow, and a diffuse-interface approach to investigate breakup and coalescence of large drops in turbulence. Both formulations will account for the effect of additives (surfactants, salts) on surface tension. To go beyond the current state of the art, we will focus on dense systems with drop volume fractions up to 50%. The simulation outcomes (e.g., breakup/coalescence efficiencies) will be then transferred for the first time at the equipment scale, where drop dispersion will be simulated without resolving the interface. This will be achieved via direct coupling of the flow solver with a population balance model, allowing for the reconstruction of the DSD from its moments. The resulting simulation tool will be made openly available to interested users. To validate the numerical results, a detailed experimental characterization of mixtures of immiscible or partially-miscible liquids, treated under different operating conditions, will be carried out in dedicated lab-scale equipment, obtaining local data from the drop scale (DSD) up to the equipment scale (concentration distribution maps) as well as global parameters (like the overall power consumption). A product of the joint numerical and experimental activities will be the development of design guidelines for novel mixing-separation equipment for liquid-liquid extraction processes.